Guiding of relatively high powers in an optical fiber may have relevance for several commercial applications such as guiding of surgical and/or therapeutic light, optical sensing, and materials processing. Among such applications are transport of optical energy and utilizing nonlinear effects in the fiber, which are commonly more pronounced with higher optical power inside the fiber. The optical power may be continuous wave (CW), pulsed or a mixture thereof. High optical power inside a fiber may be particularly pronounced with pulsed light where a high peak power may be obtainable even while having a relatively modest average power.
One limitation of the average power/spectral density carried by an optical fiber is the damage threshold of the fiber. The input facet or the first few millimeters of fiber may be destroyed if the optical power (CW, peak power or pulse energy) is above the bulk glass or glass-air interface damage threshold. It has been observed by the present inventors that even when the optical power is below this threshold, the optical fiber may still be observed to degrade over time. This degradation is often observed as increased absorption in the visible over time. For commercial applications a long lifetime may be critical.